The present invention relates to a method and apparatus for producing a photomask which is used as an original pattern at the time of fabricating micro devices, such as semiconductor integrated circuits, image pickup devices (CCDs or the like), liquid crystal display devices or thin-film magnetic heads, by using lithographic technology. This invention also relates to a method of manufacturing a device which uses such a photomask producing method.
At the time of manufacturing devices, such as semiconductor integrated circuits, a transfer system is employed which uses a photomask on which an original pattern that is a to-be-formed circuit pattern enlarged by, for example, about 4 to 5 times, and performs reduction projection of the original pattern of this photomask on a substrate to be exposed, such as a wafer or a glass plate, via a reduction projection optical system. An exposure system is used at the time of transferring the pattern of such a photomask and a photomask which is used by a reduction projection exposure apparatus of a step and repeat type is also called a xe2x80x9creticlexe2x80x9d.
Conventionally, such photomasks have been produced by writing an original pattern on a predetermined substrate (blank) by using an electron beam lithography system or a laser beam lithography system. That is, after a mask material (light-shielding film) is formed on the substrate and a resist is coated thereon, the original pattern is written by using an electron beam lithography system or a laser beam lithography system. Thereafter, the resist is developed and etching or the like is performed to form the original pattern of that mask material. In this case, given that the reduction magnification of a reduction projection exposure apparatus which uses the photomask is 1/xcex2, the original pattern that is written on the photomask can be a pattern which is the pattern of the device enlarged by xcex2, so that a writing error by the lithography system is reduced to nearly 1/xcex2 on the device. Therefore, it is possible to substantially form the pattern of a device with a resolution that is approximately 1/xcex2 times the resolution of the lithography system.
As described above, conventionally, the original pattern of a photomask has been written by an electron beam lithography system or a laser beam lithography system. Those lithography systems write the original pattern directly based on write data from a control computer. Because the areas of devices, such as recent LSIs, are getting larger, and the miniaturization scale and integration are constantly being improved, however, the original patterns of photomasks which are needed for exposure are becoming larger in area and becoming more miniaturized. While a reticle, used in double exposure, provided with a correction pattern for preventing an unnecessary pattern from being transferred, and a so-called phase shift reticle having a phase shifter provided between adjoining patterns, etc. are used as photomasks, those special photomasks tend to have a larger amount of write data than other photomasks. Because of these reticles, the amount of write data that is needed by a lithography system for producing a photomask becomes enormously large.
Therefore, the writing time required for the lithography system to write the original pattern of a single photomask recently has become 10 to 24 hours. Such increased writing times are factor in raising the manufacturing cost for photomasks.
With regard to the above, an electron beam lithography system needs to correct the proximity effect caused by the influence of scattering specific to an electron beam, and also needs to correct an uneven electric field around the substrate which is caused by charging on the surface of the substrate. To write an original pattern as designed, therefore, it is necessary to measure in advance the error of the writing position or the like under various conditions and keep performing complex correction with high precision and stability at the time of writing. It is, however, difficult to keep performing complex correction with high precision and stability, and there has been a problem of drifting of the writing position during writing. Writing may be interrupted to carry out calibration, which inconveniently makes the overall writing time longer.
When the miniaturization of pattern rules for semiconductor devices or the like advances further, therefore, the writing time for the original pattern of a single photomask will becomes too long, resulting in a variation in precision, so that the required writing precision may not be achieved. Further, the amount of write data in a control computer is becoming so large that it is difficult to use the data in single writing.
A laser beam lithography system writes an original pattern using a laser beam in the ultraviolet range and has the advantages of being able to use a resist having a higher resolution as compared with the electron beam lithography system and is free of the scatter-originated proximity effect. But, the resolution of the laser beam lithography system is lower than that of the electron beam lithography system. As the laser beam lithography system also directly writes an original pattern, the amount of write data is becoming so large as to make data processing difficult and the writing time becomes considerably long so that the required writing precision may not be achieved due to drifting of the writing position or the like.
Although a predetermined pattern may be transferred on a substrate for a photomask by using an optical projection exposure apparatus at the time of producing the original pattern of that photomask, the accuracy of the original pattern gets lower if there is a distortion in the projection optical system which is used in the execution of that transfer, a variation in the evenness of the width of the transfer line, or the like.
When a photomask is actually mounted on a projection exposure apparatus and as original pattern of that photomask is projected on a substrate, such as a wafer, via a projection optical system, there occurs the problem of exposing a deformed image on the substrate, causing an overlap error or the like, if a distortion or the like remains in the projection optical system. Because the image forming characteristics, such as any distortion of the projection optical system, slightly differs from one projection exposure apparatus to another, it is desirable to be able to correct a projection image for each projection exposure apparatus if possible.
By the way, the recent trend in the market of semiconductor integrated circuits is change towards multi-type, small quantity production type devices, called ASICs (Application Specific ICs) or system LSIs, and the demanded delivery period from the acceptance of an order for the production of such devices to the delivery is becoming very short. In manufacturing such types of devices, therefore, it is necessary to first produce a photomask (working reticle) on which the original pattern for manufacturing the devices is formed in a short period of time and then produce the devices in a short period of time by using this photomask.
State-of-the-art devices are completed through, for example, more than 20 exposure steps, and the production of even one type of devices require about the same number of photomasks as the number of exposure steps. Further, the processing performance of the aforementioned laser beam lithography system or electron beam lithography system per unit time is low, so that writing a single photomask takes more than a day in some cases. Conventionally, the original patterns of all the photomasks to be used to produce one type of devices have been written, therefore, the overall time required was considerably long and it has been difficult to shorten the production time for one type of device.
Further, because the overall writing time has been very long, the production cost for photomasks to be used in manufacturing one type of device are very high, resulting in a high production cost for the devices.
Furthermore, the types of such devices are so varied that it is becoming difficult to write the original patterns of all the photomasks to be produced, by using a laser beam lithography system or an electron beam lithography system in terms of time limitations.
It is a first object of the present invention to provide a photomask producing method which can form an original pattern within a short period of time.
It is a second object of this invention to provide a photomask producing method capable of substantially correcting a predetermined image forming characteristic of an image projected by a projection exposure apparatus which uses a photomask when the image forming characteristic is degraded.
It is a third object of this invention to provide a photomask producing method capable of substantially correcting a predetermined image forming characteristic of a projection optical system for use in a projection exposure apparatus, which is used in producing photomasks, when the image forming characteristic is degraded.
It is a fourth object of this invention to provide a photomask producing method capable of producing photomasks, which can be used in producing multi-type small-quantity production types of devices, such as ASICs and system LSIs, in a short period of time and at a low cost.
It is a fifth object of this invention to provide a manufacturing device which can implement such a photomask producing method.
It is a sixth object of this invention to provide a device manufacturing method capable of forming the pattern of a device with a high accuracy by using such a photomask producing method.
It is a seventh object of this invention to provide a device manufacturing method which can manufacture multi-type and small-quantity production type devices in a short period of time by using such a photomask producing method.
To achieve such objects, a first photomask producing method according to this invention, which produces a photomask (34) having a transfer pattern (27) formed, segments an enlarged pattern of the transfer pattern (27) into patterns of plural parent masks (R1 to RN); and sequentially transfers reduced images of the patterns of the plural parent masks (R1 to RN) onto the surface of a substrate (4) for the photomask by performing screen linkage (e.g. seamless stitching exposure, etc.).
According to this invention, at the time of producing a photomask, as one example, a thin film of a mask material is formed on a photomask substrate (4) and a photosensitive material such as a photoresist is coated on the film. Then, after reduced images of a plurality of parent masks are transferred on a photosensitive material by a step and repeat system or a step and scan system using, for example, an optical and reduction projection type exposure apparatus, the photosensitive material is developed. Then, a desired transfer pattern (original pattern) is formed by executing etching or the like with the pattern of the remaining photosensitive material as a mask.
At this time, given that the reduction magnification of, for example, an optical exposure system for producing a photomask is 1/xcex1 (xcex1 being an integer, a half integer or the like greater than 1), a transfer pattern (27) or an original pattern is enlarged by xcex1 and this enlarged parent pattern (36) is segmented into patterns of xcex1xc3x97xcex1 parent masks lengthwise and breadthwise. As a result, the pattern which is formed on each parent mask is a part of a parent pattern which is an original pattern enlarged by xcex1, so that the amount of write data of the pattern of each parent mask is reduced to about 1/xcex12 of the conventional amount and the minimum line width becomes xcex1 times the conventional width. Therefore, the pattern of each parent mask can be written with a high precision and less drift in a short period of time by using, for example, a conventional electron beam lithography system or laser beam lithography system. Further, the writing error of the lithography system is reduced to 1/xcex1 on a photomask and the accuracy of the original pattern is further improved. Further, once those parent masks are produced, the patterns of the parent masks can be transferred quickly on a photomask substrate by a step and repeat system or the like, so that the production time for producing a plurality of photomasks, particularly, can be shortened significantly as compared with the conventional system that writes them individually by a lithography system.
The term xe2x80x9cscreen linkagexe2x80x9d means linking different areas on an object onto which patterns are transferred to form a device pattern in the linked areas on the object by exposure of the different areas, and the exposure operation to link the different areas on the object is called xe2x80x9cstitching exposurexe2x80x9d (step and stitch type). The term xe2x80x9cscreen linkagexe2x80x9d (stitching exposure) in this specification includes not only the meaning that individual reduced images of parent masks obtained by segmenting a single pattern are linked together to complete the single pattern to be transferred to a photomask, but also means that a plurality of parent masks are formed without segmenting a single pattern and the individual reduced images of those parent masks are linked together to complete a photomask having a plurality of patterns. In short, the term xe2x80x9cscreen linkagexe2x80x9d (stitching exposure) in this specification is used to simply mean the linkage of the individual reduced images of parent masks together, regardless of whether or not a single pattern is formed by linking screens (stitching exposure). In the case of forming, for example, a photomask having a plurality of patterns, therefore, possible ways for the segmentation for parent masks include the segmentation of one of the patterns into a plurality of parent masks and the segmentation into a plurality of parent masks without segmenting each pattern. The former case is advantageous in that the shapes (sizes) of parent masks can be made uniform, and the latter case is advantageous in that there is no pattern joint so that defects such as improper linkage do not occur.
Next, a second photomask producing method according to this invention, which produces a photomask (34) on which a transfer pattern is formed, segments the transfer pattern (27) or an enlarged pattern (36) thereof into N sets (N being an integer equal to or greater than 2) of patterns of plural parent masks (R1 to RN, Q1 to QN); and sequentially transfers reduced images of the N sets of patterns of plural parent masks onto the surface of a substrate (4) for the photomask while performing screen linkage (stitching exposure).
According to this invention, at the time of producing a photomask, as one example, a thin film of a mask material is formed on a photomask substrate (4) and a photosensitive material such as a photoresist is coated on the film. Then, after the images (or reduced images) of N sets of plural parent masks are transferred, one on another, on a photosensitive material by a step and repeat system or a step and scan system using, for example, an optical and reduction projection type exposure apparatus, the photosensitive material is developed. Then, a desired transfer pattern (original pattern) is formed by executing etching or the like with the pattern of the remaining photosensitive material as a mask.
At this time, multiple exposures of the patterns of N sets of parent masks allow the writing error of the patterns of the parent masks to be averaged by the number of multiple exposures, making it possible to significantly reduce the line width error, positional error or the like of a transfer pattern (original pattern) on a photomask. Further, once those parent masks are produced, the patterns of the parent masks can be transferred quickly on a photomask substrate by a step and repeat system or the like, so that the production time for producing a plurality of photomasks, particularly, can be shortened significantly as compared with the conventional system that writes them individually by a lithography system.
Given that for example, an optical exposure system for producing a photomask provides 1/xcex1 reduction projection, a transfer pattern (27) is enlarged by xcex1 and this enlarged parent pattern (36) is segmented to patterns of one set of xcex1xc3x97xcex1 parent masks lengthwise and breadthwise. Likewise, the pattern of a parent mask in another set is a part of its enlarged segmented parent pattern (36). Consequently, as in the above-described first photomask producing method, the amount of write data of the pattern of each parent mask is reduced to about 1/xcex12 of the conventional amount and the minimum line width becomes xcex1 times the conventional width. Therefore, the pattern of each parent mask can be written with a high precision and less drift in a short period of time by using, for example, a conventional electron beam lithography system or laser beam lithography system. Further, the writing error of the lithography system is reduced to 1/xcex1 on a photomask and the accuracy of the original pattern is further improved.
In this case, one example of the patterns of N sets of plural parent masks are a plurality of patterns segmented from the transfer pattern or an enlarged pattern thereof in the same arrangement. Multiple exposures of the pattern images of parent masks that are segmented in the same arrangement this way allow the writing error of the lithography system for writing those parent masks to be averaged and become smaller.
It is desirable that a segmenting method for at least one set of patterns of plural parent masks (BI1 to BI26) in the N sets of patterns of plural parent mask patterns should differ from that for another predetermined set of patterns of plural parent masks (PI1 to PI26). With the segmenting method changed this way, pattern images to be subjected to multiple exposures on the photomask substrate undergo multiple exposures at different positions in the exposure area of the projection optical system which projects the pattern images of their parent masks. Therefore, the distortion of the projection optical system and errors in the evenness of the width of the transfer line at a position in the exposure area are averaged and the precision of the patterns of the photomasks is improved.
It is desirable that at least one set of patterns of plural parent masks in the N sets of patterns of plural parent masks should include a linkage area for another predetermined set of patterns of plural parent masks. Accordingly, linkage errors at the time of performing stitching exposure while performing screen linkage is averaged and is reduced.
Next, a third photomask producing method according to this invention, which produces a photomask having a device pattern, transfers one (P1 to PN) of a plurality of segment patterns segmented from an enlarged pattern of the device pattern onto a mask substrate (4), and transfers another segment pattern (A1 to AN) which is the same as the one segment pattern at least partially on the mask substrate (4) in such a way that the same portions overlap each other.
According to this invention, provided that those segment patterns are to be written by an electron beam lithography system or the like, the writing error of two segment patterns is averaged by exposing two segment patterns, one on the other, so that the accuracy of the device pattern is improved. Further, as those segment patterns can be repeatedly used by a step and repeat system or the like, multiple photomasks can be produced at a high speed.
In this case, it is desirable that the plurality of segment patterns should be exposed with a light beam and their reduced images should be transferred and linked together, on a predetermined mask substrate (4). This reduction projection decreases the writing error of those segment patterns on the photomask, so that the precision of the device pattern is improved.
It is also desirable that at the time of sequentially transferring reduced images of patterns of the plural parent masks (R1 to RN) on the surface of the substrate (4), a reduction projection exposure apparatus of a static exposure type or a reduction projection exposure apparatus of a scanning exposure type should be selectively used in accordance with the use of the photomask (the system of the exposure apparatus to be used or the like). When the photomask is used in a reduction projection exposure apparatus of a scanning exposure type, such as a step and scan system, distortion of a parallelogram shape (so-called skew error) may occur in a projected image. In this case, it is difficult to correct a skew error in a static exposure type, so that at the time of transferring patterns of a plurality of parent masks on the substrate for the photomask, the distortion at the time the photomask is used can be reduced by adding such a distortion as to cancel out the skew error by using a projection exposure apparatus of a scanning exposure type. This makes the overlapping error or the like smaller.
Further, it is desirable that at the time of sequentially transferring patterns (or reduced images of patterns) of the plural parent masks (R1 to RN) on the surface of the substrate (4), each of the image forming characteristics (transfer position, magnification, distortion, etc.) of the reduced images of the patterns of the parent masks should be corrected in accordance with at least one of the rotational asymmetric aberration and the distortion characteristics of the projection optical system (42) of a projection exposure apparatus which uses the photomask.
If the amount of a variation in a predetermined image forming characteristics of an exposure system which uses a photomask is known in advance, the distortion or the like of a device pattern to be exposed finally using the photomask becomes smaller and the overlapping precision or the like is improved by adjusting the transfer position, magnification and also distortion or the like of the pattern images of the individual parent masks in such a way as to cancel out the amount of variation in the image forming characteristics at the time of transferring the pattern images of the individual parent masks on the substrate for a photomask while performing screen linkage (stitching exposure).
With regard to that, there may be a case where multiple photomasks are produced and those photomasks are used in a plurality of projection exposure apparatuses by a mix and match system or the like. In this case, it is desirable to adjust the transfer position or the forming characteristic or the like at the time of transferring the patterns of the individual parent masks, linked together, in accordance with the average characteristic of the distortion characteristic or the like of projection images of at least two predetermined projection exposure apparatuses which use those photoresists, so that the individual projection exposure apparatuses can acquire excellent overlapping precision.
Next, it is desirable that a photomask be further used in reduction projection. Assuming that a photomask is used in reduction projection of, for example, 1/xcex2 (xcex2 being an integer, a half integer or the like greater than 1) and the reduction magnification of an exposure system for producing a photomask is 1/xcex1 (xcex1 which, like xcex2, is an integer, a half integer or the like greater than 1), the writing error of the patterns of the individual parent masks is reduced to 1/(xcex1xc2x7xcex2) on a device pattern to be finally exposed. Even if the minimum line width of the device pattern is set to xc2xd of the current width, therefore, it is possible to write patterns (segment patterns) of the individual parent masks with the required accuracy easily and in a short period of time by using an electron beam lithography system or a laser beam lithography system or the like. Even when the pattern rules are miniaturized further, therefore, a desired device pattern can be exposed with the needed precision.
A part of those parent masks (segment patterns) may be used as a phase shift reticle or the like. Further, it is desirable to optimize the image forming characteristic for each parent mask.
A fourth photomask producing method according to this invention, which produces a photomask (WR) having a predetermined transfer circuit pattern formed, forms a parent mask (MR1) formed with a predetermined pattern including one or a plurality of pattern units (Pa, PB, Pc) respectively corresponding to one or a plurality of circuit blocks in the transfer circuit pattern; and transfers a projection image of the pattern unit selected from a pattern of the parent mask (MR1) on a substrate (50) for the photomask (WR) in a predetermined positional relation.
According to this invention, in the case of producing photomasks (working reticles) for plural types of devices of multi-type small-quantity production type, such as so-called ASICs and LSIs, the photomasks should be produced for each type. However, not all of the to-be-transferred patterns (patterns of working reticles) for those plural types of devices differ type by type but they often have common circuit blocks, such as a CPU section and RAM section, even among different types of device. Even different types of devices, which do not have a CPU section or RAM section, typically have some kind of common circuit blocks (small-scale circuit units) which are smaller in scale than the CPU section or the like.
According to the fourth photomask producing method of this invention, therefore, a pattern unit corresponding to a predetermined circuit block in a pattern to be formed on a photomask is formed in advance. Then, a mask material is formed on a substrate (50) for that photomask and a photosensitive material is coated on-that mask material. After that, the projection image of the corresponding pattern unit in that parent mask is transferred to a position on that substrate where the circuit block is to be formed, and at other portions, corresponding patterns are transferred or written. Then, the photosensitive material is developed and etching or the like with the remaining photosensitive material as a mask is carried out. Accordingly, the photomask is produced in a short period of time and thus at a low cost.
In this case, as one example, the circuit block corresponds to one of a CPU core section, RAM section and ROM section in an integrated circuit and standard circuit block for a standard cell. In general, ASICs or the like often commonly have a CPU section or a RAM section or the like, so that parent masks according to this invention can be commonly used at the time of producing photomasks (working reticles) that are used in manufacturing many types of devices and can thus reduce the manufacturing cost of each device.
It is desirable that as the parent mask, plural parent masks (MR1, MR2) should be prepared on which different pattern units (Pa, Pf) respectively corresponding to different circuit blocks in the transfer circuit pattern are formed; and projection images of the pattern units selected from patterns of the plural parent masks should sequentially be transferred on the substrate (50) for the photomask in a predetermined positional relation. This transfer of a combination of the projection images of the pattern units of plural parent masks can manufacture many types of devices in a short period of time using fewer parent masks as a whole.
That is, it is desirable that the parent mask (MR1) be used at the time of producing plural types of photomasks (WR, WR1). This can shorten the production period for each photomask and can thus reduce the production cost.
For devices such as a new type of ASIC, parent masks (master reticles) having new circuit portions should newly be produced. Because the patterns of most of the circuit blocks of such a new type of devices are formed by exposure and transfer of pattern units of existing parent masks and the number of pattern units that should be written on new parent masks can be small, it is possible to considerably shorten the production time and cost for photomasks for the new type of devices.
It is also desirable that the reduced image of the pattern unit of the parent mask should be transferred on the substrate for the photomask; and the photomask should be further used in reduction projection. When the pattern of a parent mask is used in reduction projection of, for example, 1/xcex1 (xcex1 being 4 or 5 or the like, for example), the writing error of the pattern of the parent mask on the photomask also becomes 1/xcex1 as mentioned above. In writing the pattern to that parent mask, therefore, it is possible to use a lithography system, such as a laser beam lithography system, which has a higher throughput than that of an electron beam lithography system. As the photomask is used in further reduction projection, the influence of the writing error of the pattern of that parent mask is further reduced, making it possible to manufacture finer devices with a high accuracy.
Further, by using an exposure beam stopped down to a predetermined spot, a part of the transfer circuit pattern may be written on the substrate for the photomask at at least a part of an area other than where the image of the pattern unit of the parent mask is transferred. The pattern of that photomask may include lines for connecting basic pattern units or a small-scale pattern or the like specific to each device. It is troublesome in some cases to produce a mask which has such lines and small-scale patterns or the like as new pattern units. In such a case, the production times for various kinds of photomasks can be shortened and the production costs can be decreased by forming only the lines and small-scale pattern by writing with a laser beam or the like.
Next, a photomask producing apparatus according to this invention comprises a mask retaining unit (16 to 18) for retaining a plurality of masks (R1 to Rn); a mask stage (2) on which a mask selected from the mask retaining unit is placed; a projection optical system (3) for projecting a reduced image of a pattern of the mask on the mask stage onto a substrate (4) for a photomask; a substrate stage (6) for positioning the substrate on a plane perpendicular to an optical axis of the projection optical system; and an alignment system (14A, 14B) for aligning the mask on the mask stage (2) with the substrate on the substrate stage (6) in order to transfer reduced images of patterns of the predetermined masks on the substrate, shifted from one another.
The use of this photomask producing apparatus can implement the photomask producing method of this invention.
In this case, as one example, the mask retaining unit retains plural parent masks (R1 to RN) on which segmented patterns of an enlarged pattern of a pattern (27) of a photomask to be produced are formed. Accordingly, those parent masks can be exchanged at a high speed and exposure can be carried out in a short period of time.
Further, it is desirable that this photomask producing apparatus should comprise a view field selecting system (104) for selecting a pattern of a predetermined shape at an arbitrary position in the patterns of the masks and projecting a reduced image of the selected pattern by the projection optical system on the substrate (50) for the photomask; and the alignment system (109A, 109B, FM1) aligns the mask with the substrate on the substrate stage in order to transfer the reduced image selected by the field view selecting system on the substrate in a predetermined positional relation.
Further, it is desirable that the producing apparatus should be provided with an exposure beam irradiation system (LA1, AM1, 121, 120) for irradiating an exposure beam (laser beam, electron beam or the like) stopped down to a spot on a desired portion on that substrate. A circuit pattern such as lines which is not appropriate for transfer from that mask can easily be formed by writing with an exposure beam.
A method of manufacturing a device for forming a predetermined pattern on a substrate (W), according to this invention, segments a second pattern (36) obtained by further enlarging an enlarged first pattern (27) of the predetermined pattern into patterns of plural parent masks (P1 to PN); produces a photomask (34) for real exposure formed with the first pattern (27) by performing reduction projection of the patterns of plural parent masks on a predetermined substrate (4), sequentially shifting their positions from one to another; and transfers a reduced image of a pattern of the photomask for real exposure on the substrate (W).
According to this invention, assuming that the magnification from the pattern of a device to be formed on the substrate (W) to the first pattern (27) is xcex2 (xcex2 being an integer, a half integer or the like greater than 1) and the magnification from the first pattern to the second pattern (36) is xcex1 (xcex1 which, like xcex2, is an integer, a half integer or the like greater than 1), the line width of the patterns of those parent masks becomes xcex1xc2x7xcex2 of the line width of the patterns of the device. If the writing error of the line width at the time of writing the patterns of those parent masks with an electron beam lithography system or the like is xcex94d, therefore, the error of the line width of the patterns of the device is reduced to approximately xcex94d/(xcex1xc2x7xcex2), so that the patterns of the device can be formed with an extremely high precision.
With regard to the device manufacturing method, it is preferable that the second pattern (36) of the parent mask should be segmented to N sets (N being an integer equal to or greater than 2) of plural patterns (P1 to PN, Q1 to QN); and the photomask (34) for real exposure formed with the first pattern (27) should be produced by performing reduction projection of the N sets of patterns of plural parent masks on a predetermined substrate (4) while sequentially performing screen linkage (stitching exposure).
Accordingly, as the reduced images of N sets of patterns of parent masks are transferred, overlapped one on another, the averaging effect reduces the effect of the writing errors of the lithography system and the distortion or the like of the projection optical system for performing reduction projection of patterns of parent masks.
Next, a method of manufacturing a device for forming a predetermined circuit pattern on a substrate, according to this invention, forms a pattern unit (pa) corresponding to at least one circuit block in an enlarged first circuit pattern of the predetermined circuit pattern on a parent mask (MR1); produces a photomask (MR) for real exposure formed with the first circuit pattern by transferring the pattern unit of the parent mask on a predetermined substrate (50) in a predetermined positional relation; and transfers the reduced image of a pattern of the photomask for real exposure on a substrate (W) for the device.